Evidence that fucosylated glycoconjugates play a significant role in brain development is suggested by reports of severe mental retardation in patients that lack fucose residues. However, the mechanisms by which fucosylated glycoconjugates influence brain development are not known. The epitope 3-fucosyl-N-acetylactosamine (SSEA-1) is an excellent candidate to play a vital role in brain development, both because it is expressed in developing brain with temporal and spatial specificity, and because it has been shown to have a key role in cell-cell interactions in other tissues. Thus, we postulate that SSEA-1 plays a key role in the cell-cell interactions required for normal neural development. Our preliminary results indicate that SSEA-1 glycolipid expression in neonatal cerebellum correlates with granule cell migration, and the goal of this project is to elucidate the role of these molecules in this process. Specifically, we will characterize and measure SSEA-1 glycosphingolipids and proteins in developing rat cerebellum and relate these data to the stage and regional immunohistochemical appearance of this antigen. We also will characterize the fucosyltransferase activities involved in SSEA-1 glycoconjugate synthesis during cerebellar development, as our data suggests fucosyltransferase(s) play a critical role in controlling SSEA-1 glycolipid expression. Simultaneously, we will characterize the genes responsible for these fucosyltransferase activities and evaluate their regulation during development. Results obtained from these studies will then enable us to investigate the biological role of SSEA-1 glycoconjugates. We propose to determine whether overexpression, or blocking the accessibility, of SSEA-1 antigens in the neonatal cerebellum would result in anomalous behavior of developing granule cells. To cause over expression of SSEA-1, we propose to inject intracerebrally neonatal rats with AAV vectors carrying an epitope-tagged form of the relevant cloned rat fucosyltransferase under the control of a strong non-tissue specific promoter. To block the function of SSEA-1, we plan to inject irradiated hybridoma cells producing anti-SSEA-1 antibodies. These brains will then be examined histologically during subsequent development to establish the degree of fucosyltransferase and SSEA-1 expression and to determine whether perturbing SSEA-1 expression or availability changes the normal pattern of granule cell migration, parallel fiber extension and/or synaptogenesis.